Drying apparatus



H. B. LOWDEN. DRYING APPARATUS:

APPLICATION FILED JAN. 7, (920.

1,377,896. Patented y 10 1921,

4 SHEETS-SHEET I.

avwem tot H. B. LOWDEN.

DRYING APPARATUS.

APPLICATION FILED JAN. 7, 1920.

Patented May 10, 1921.

4 SHEETS-SHEET 4.

anvemfoz HUGH B. LO'WDEN, 0F DENVER, COLOBADD.

DRYING APPARATUS.

Specification of Letters Patent.

Patented May it), 1921.

Original application filed October 22, 1917, Serial No. 197,805. Dividedand this application filed Jannary 7, 1920. Serial No. 349,988.

T 0 all whom it may concern:

Be it known that 1, HUGH l3. LOWDEN, a citizen of the United States,residing in the city of Denver, State of Colorado, have invented certainnew and useful Improvements in Drying Apparatus, of which the followingis a specification.

This application is a division of an application filed by me in theUnited States Patent Oflice on the 22d day of October, 1917, Serial No.197,905.

My present invention relates to an apparatus for drying or partiallyeliminating moisture from materials, and is designed to afford simple,efiective and economical means for drying materials, particularly suchas could not be handled satisfactorily in driers of preexisting types,or if so handled, would suffer serious dust losses or injury to thequality of the product.

As an example of the class of material to which my present invention isespecially adapted, I mention flotation concentrates, obtained in thetreatment of ores. This product is customarily dewatered on continuousrevolving drum vacuum filters, but after such dewatering, still retainssuflicient moisture to render it plastic, which occasions seriousdifficulty in subsequent treatment, such, for example as theimpossibility of so mixing it with other, usually dry, ingredients as toproperly incorporate it in a suitable charge for sintering. Where theflotation concentrates from their nature, are preferably roasteddirectly, as in multiple hearth roasting furnaces, their high moisturecontent reduces the capacity of the furnaces, and their cohesive andadhesive qualities cause them to interfere with the normal operation ofthe rabbling means, as also to ball 'up and resist proper exposure tothe air,

The difficulties above alluded to are new ones, in that they werepractically non-e2;-

istent prior to the advent of the flotation process. Novel means wererequired to meet them and the invention herein described discloses athoroughly satisfactory apparatus for overcoming them. However, myinvention is equally well adapted to other products which haveheretofore been difficult to dry on a large scale.

I dry the product mentioned, or other material, by feeding it to aheated surface and operating upon it in such a manner that there is noloss from dusting, no interference with bustion, which is objectionablewith certain classes of material.

One or more of the above defects is present in all preexisting driers ofwhich I am aware. Direct heat driers carry off a prohlbitive amount ofdust in operation, and also permit the contamination of the material bythe products of combustion. All revolving cylinder driers are subject tooperatmg diihculties due to plastic material adhering to their interiorsand to balling up of the cohesive material. Drying upon hearths rabbledby chain dragged rabbles is attended by the discharge of undriedmaterial which has adhered to the rabbles; and, if the clogging 1sextensive, by the sweeping of all or a large part of the materialundried from the hearth. Drying upon hearths over which the material isadvanced by so-called grasshopper conveyer mechanisms is of very lowefliciency, due to material remaining upon the hearth and not beingremoved owing to the arcuate paths described by such mechanisms, and tothe fact that such mechanisms do not break up masses of adhesivematerial, but tend to ball it up and push or roll the masses overthehearth.

The first of the latter two defects prevents efficient heat transferencefrom the hearth to the material, and the second impedes the escape ofmoisture from the material into the atmosphere.

The operation of these machines differs essentially from that of myapparatus in that they do not include the distinct subdividing ofcohesive masses of material, whereas my machine efl ects the repeatedcutting of such masses, thereby exposing fresh surfaces and preventingthe material from baking in hard lumps from which moisture is veryslowly eliminated. As a result of this, satisfactory operations of allsuch methods is limited to granular materials having little or nocohesive and adhesive properties. This is commonly recognized, and suchdriers, owing largely to the absence of definite break-up action intheir methods of operation are generally regarded unsuit able for dryingflotation concentrates, and, so far as I am aware, flotationconcentrates are not dried by any of them in practice.

For efiiciently drying the class of mate- 'rials referred to, I havefound it necessary to use a hearth surmounting a flue through which Ipass the heated gases of combustion as from a firebox, or waste heatedgases from some other operation, if available, but this hearth is arepresentation of any drying surface however heated, and in fact, myhearth may consist of a jacketed pan through which exhaust or live steamis passed, or of any surface heated by other means. Under certainconditions a mufl'le might be preferable to a hearth, and such a mufflemight be heated from without, air, or heated air or gases being forcedor drawn through the interior of the muflie or not, or the only heatapplied might be through the medium of heated air or gases passedthrough the muflie.

The drying might be accomplished, either upon a hearth or within amuffle, by mere exposure to the atmosphere, without the application ofheat, when, for example, the material would be injured by an elevatedtemperature.

In describing my apparatus I shall confine myself to a hearth heatedfrom beneath, as the operation in a muffle or upon any other surfacewill be readily understood therefrom.

I feed the material upon the hearth at one end, and operate upon it by alarge number of plows, or rabbles, which conveniently actsimultaneously. I move this series of rabbles, which collectively Idesignate a rake, by mechanical means, forward as closely to the hearthas practicable; I then raise them out of contact with the material onthe hearth in a substantially vertical direction so that there is notendency of the rabbles to drag over or compress the material. I thenmove them backward out of contact with the material on thehearth, andnext lower them into the material so that they cut into the masses leftby the preceding forward stroke. This is one cycle of the operationwhich proceeds continuously as long as power is applied,and

it will be seen that there is no possibility of undried material beingdischarged, as any masses which adhere to the rabbles will fall backupon the hearth at or near the point from which they are lifted.

I append hereto drawings illustrating my preferred form of apparatus,the various parts being designated by reference characsuitable guides inthe blocks ters, the same reference character indicating the same orcorresponding part in the various figures.

In the drawing:

Figure 1 represents a transverse section through the hearth, flue, rakeand operating mechanism.

Fig. 2 is a longitudinal section on theline 2-2 of Figs. 1 and 3.

Fig. 3 is a plan of the operating mechanism.

Fig. 4 shows another mechanism for securing a suitable rectilinearmotion in four directions.

Fig. 5 is a detail of my preferred hearth construction.

Fig. 6 is a transverse sectional elevation of my rabbling means embodiedin a muflie.

Figs. 7 and 8 are details of the last named.

Figs. 9 to 12 inclusive are details of an attachment to the rake.

Fig. 13 shows my preferred arrangement of the rabbles.

In Fig. 1,the hearth composed of cast iron plates, is shown at 1. Theserest upon longitudinal side walls. 2, with which they form a flue,through which heated gases, as from a fire-box, are passed for thepurpose of heating the hearth. The bottom of this flue may be paved, asindicated at 3. The rake, 4, is studded with plows or rabbles 5, and isadapted to operate in connection with the hearth. Piers 6 areshownsupporting the rake operating mechanism.

In Fig. 2 the hearth is shown at 1, the rake at 4, with its rabbles 5.At 7 are bearings fixed to the tops of the piers 6 of Fig. 1. 8 is a baradapted to slide lengthwise in the bearings 7, 9 are blocks fixed uponthe bar 8. 10 are bearings fixed upon the bar 8 so as to move with itand receive the rock shafts 11. The rock shafts 11 carry arms 12 and 13,ex-

tending substantially at right angles to each other and forming ineffect a bell crank. The arms 12 carry the rake at their free ends bythe uprights 14 and 14 and by the vertical oscillation of their freeends effect the raising and lowering of the rake.

At 15 is shown a shaft, the rotation of which operates the rakemechanism, through the crank 16, which communicates a reciprocatingmotion to the connecting rod 17. The rod 17 is connected at its otherend to a crosshead 18, which is adapted to reciprocate in 9. Thereciprocation of the crosshead with respect to the blocks 9 is limitedby the set screws 20.

The extent to which the crosshead can reciprocate in the blocks 9 isless than the stroke of the connecting rod 17 and after it has beenmoved to the limit fixed by the set screws 20, further motion of theconnecting rod will cause the bar 8 to slide in its bearponents of myrectangular motion.

The vertical components of my motion are efiected by the connection ofthe crosshead with the arm 13, by the rod 21, which converts thereciprocating motion of the crosshead into an oscillating motion of therock shaft.

The operation of the mechanism is therefore as follows;

Power is applied to rotate the shaft 15, which through the crank 16,causes the bar 17 to reciprocate. The first effect of thisreciprocation, assuming it to be toward the left (in Fig. 2) is to drawthe upper end of the arm 13 toward the left, thus depressing the arm 12and forcing the ralre down into the material on the hearth. Thismovement is interrupted by the set screw stop 20 after which the strokemoves the bar 8 with all its attached parts, including the rake, towardthe left until the crank 16 reaches the dead center.

After passing the dead center, the connecting rod. 17 will move towardthe right, first sliding the crosshead in its guides and raising therake until the crosshead engages the set screw, then pushing the raketoward the right in its upper plane of travel. and out of contact withthe material on the hearth. This completes one revolution of the shaft15-or one cycle.

As above indicated, the set screws 20 control the extent of the verticalcomponent of he rectangular path described by the ralre. In practice, Iallow ample lift, and use the excess to regulate the horizontalcomponent. The set screw 20 at the left, in 2, should be so adjustedthat the rake will operate as closely as possible to the hearth on thefor ward stroke. The set screw shown at the right controls the height towhich the ralre is lifted, and an excess over what is really necessaryis without effect on the operation. Therefore, this set screw is used tofix the length of the forward stroke, so that the rabbles on risingleave themasses of material at the proper points for the rabbles onagain descending to cut into and effectively subdivide them. p

lt will be understood that although I have described my mechanism andits operation by reference to a single set of the es tial elen'ients, lin fact make use of more than one set.

Thus in 2 and 3 toe rake has four points of support, corresponding towhich there are four bell cranks on two rock shafts. The bell cranksobviously should oscillate in unison, and this may be convenientlyprovided for by connecting the arms 13 by the rods 22.

lln practice, I counterbalance the ralre by counterweights indicated at23.

1 preferably construct my rake of longitudinal. members 24.- to w richtransverse bars 25 are fixed at intervals. The transverse bars bear therabbles 5 which ll make of sheet metal.

In the mechanism just described, the vertical components of therectangular movement are not strictly vertical, that is straight linemovements, but through an arc of which the rock shaft is the center.However, the bell crank principle is exceedingly-simple and convenientand I have found in practice that the slight departure from a truestraight line is wholly immaterial.

' show, in l, means for obtaining a truly straight line rectangularmotion, this figure including only the parts which would talre the placeof the bell cranlr of 2.

ln said Fig. i, 8 is the reciprocating bar, as is the longitudinalmember of the ralre, and 14: is the rake upright. A vertical guide bar26 is attached to the reciprocating bar, as by the set screw 27, and theralre upright is furnished with parts 28 encircling the guide bar whichpermit it to move only vertically on the guide bar. 29 is a toggle,connecting the rake upright with the bar and 21 is the connecting rodattached at the end shown to the knee of the toggle, and at the otherend to the crosshead. A pull on the rod 21 will raise the rake and apush will lower it.

Fig. 5 is a partial longitudinal section through the hearth, showing howl form the pans which compose Expansion and contraction in a long hearthis considerable, and bolting the sections together would beunsatisfactory on that account. l malre the individual sectionsof thehearth to lap, one

over the other, as 30, and l bevel the edges as at 31, so that anymaterial which may have collected in the space between them will, uponfurther expansion due to higher heating, be forced upward and out of thejoint and prevent one section from tending to displace the aojoiningone. 32 are strengthening ribs, and 33 is a lug in the center of eachside of tie hearth pan. This lug 33, rests in a small anchor plate 34E(also shown in Fig. 1) which it fits snugly in a directionlongitudinally of the hearth, but sufliciently loosely in a transversedirec- "ion to permit expansion to be accommodated for. Thus eachindividual hearth plate can expand or contract transversely by the lugsliding longitudinally by the edge of one plate, sliding upon the other,lug 33 hold' the center of each plate and. consequently the entirelength of the hearth fixed.

Fig. 6 shows apparatus for conducting the operation in a muffle. Inthis, continuous walls 85 replace the piers (6 in 1), and a hood 36forms with the walls muffle.

The hood of the niuliie, T provide with slots 37, through which the rockshafts extend. The special features of these slots are shown in Figs. 7and 8. Fig. 7 is a side in the anchor plate, and

elevation of a small part of the hood, and Fig. 8 is a transversesection on the line AA of Fig. 7.

To prevent excessive leakage through the slot I provide a cover plate 38carried by the rock shaft which has a working fit in the boss 89. Theplate is retained by the lugs 40, but is free to slide forward andbackward with the rock shaft.

The material to be dried may be fed to the hearth automatically in theform of the discharge from a revolving drum filter, in which case it mayconveniently fall to it over the apron plate 41 of Figs. 9, 10, 11 and12. Material in a certain physical condition will have a tendency tofall and remain upon the rake bars at this point, and I provide adeflector 42 attached to the rake by the hinge 43. This deflector isfree to move within limits fixed by'the length of stroke of the rake andthe position of the stationary pins 44 and 45.

In Fig. 9 the rake is shown at the completion of the backward stroke,before it has been lowered. In this position the deflector rests uponthe pin 45 and will catch any material which in its absence would fallupon the rake. Fig. 10 shows the rake after the lowering movement, thedeflector still resting upon the same pin and shielding the rake. i

As the rake moves forward, that is toward the right, the lower end ofthe deflector Will be carried with it, and the upper end will ride uponpin 45 until the center of.

gravity of the deflectorwith its load passes to the right of pin 45,whereupon it will fall upon pin 44 and the jar it thereby receives willshake off adhering material. This position of the parts is representedin Fig. 11.

Fig. 12 shows the rake after completion of the rising movement andbefore the backward stroke has commenced. The deflector is still restingupon the pin 44 and will continue to do so until the hinge passes to theleft of it, when it will fall upon pin 45, and at completion of thestroke be again 1n the position shown in Fig. 9.

In Fig. 13, I show a detail of my preferred rake construction. Thefigure is a plan of a small section of my rake, and shows the manner inwhich I dispose the rabbles 5 on the transverse rabble bars 25 topositively effect the subdividing or cleaving of the material beingdried. Adjacent bars carry alternately right-hand and left-hand rabbles;thus, if those on the bars 25 are designed right-hand, those on 25 willbe left hand.

The rabbles, moving forward, will each push along what material is infront of them, and when they are raised, will leave it in small massesupon the hearth. Now I so proportion the distance between the rabblebars and the length of the stroke of the rake, that upon again enteringthe material they do not enter the spaces left by the previous stroke,but enter these masses and cleave them; the repetition of this actionsoon accomplishing a thorough subdivision of the material.

If the conveying movement of the rake is assumed to be upward inthe'plane of the paper, in Fig. 13, and the rake is assumed to havecompleted the conveying stroke, it will next rise, and after completingthe return stroke, descend into the material, the rabbles on 25 enteringthe piles of material left by the rabbles on 25, thereby cutting themopen and exposing fresh surfaces.

In practice,-more or less material, if adhesive, clings to the rabbles;but this does not interfere with the satisfactory operation of themachine, because owing to the action of the rake being a reciprocatingone, the material so attached to the rabbles will eventually fall backupon the hearth in substantially thesame place it was lifted from, andcannot be discharged undried.

When operating upon adhesive material, there is little or no actuallowing action at the feed end of the heart due to the obliquity of therabbles, nor is this essential at that stage of the drying, the choppingup of the masses being there most important. However, after the materialhas lost a portion of its original moisture, and has become thoroughlysubdivided, the rabbles do then push it sidewise aswell as forward andthis action effectively exposes all parts of it to the heat of thehearth and to the atmosphere. I attach the rabbles 5 adjustably, so thattheir angles with the rabble bars can be changed, and the rake caused toconvey the material rapidly or slowly, sired. v i

The rake, operating immediately above the hearth, is subjected to ahigher temperature than the reciprocating bars 8 and to permit theunequal expansion of these parts, make a rigid attachment to but one endof the rake, that being shown at 14. Other supports I connect by links14 connected to both rake and arm 12. This adapts such link 14 to liftand lower and causes the reciprocation to be communicated to the rake bythe rigid upright 14. This provision prevents unequal expansion from setting up strains and promotes smoothness of operation. It also eliminatesvibration which a long rake would be subjected to if rigidly connectedat all points of support.

The operation of my method of drying is carried out by use of the hereindescribed apparatus as follows:

Heat is continuously communicated to thev hearth, and the materialdelivered upon it, preferably also continuously, as by allowing it tofall directly from the discharge of a drum filter. The feed end, in thedrawings as may be de revneee forming part hereof, is the end remotefrom the driving mechanism.

Assuming the rake to have completed the backward or return stroke, itdescends into the material, the rabbles cutting the lumps or ridges ofmaterial left by the rake upon rising for the return stroke. Forwardmovement of the rake now takes place closely to the surface of thehearth, each rabble pushing forward and sidewise the material in itspath. The rake next rises and then returns to the backward limit of itsstroke, moving in a plane above and out of contact with the material onthe hearth, this completing one cycle.

The material being thus moved through but a small portion of the lengthof the hearth by one stroke of the rake, requires considerable time inpassin over its entire length and is subjected to the cleaving andplowin action of the rabbles repeated many times.

the nature of the material and amount of moisture in it, as well as withthe extent to which the moisture must be eliminated. The time it willremain on the hearth can be regulated by the speed of revolution of theshaft 15 and by the angle at which the rabbles are set. Thus the speedand the rate of feed being unchanged, a thin bed of material movingrapidly or a deep bed moving slowly may be maintained, depending uponwhether the rabbles are slightly or steeply inclined to the longitudinalaxis of the hearth.

What I claim is:

1. In combination drying surface, means for feeding material thereto ina layer or stratum and means for cleaving it at a plurality of isolatedpoints in a substantially vertical direction, pushing the cleavedportions lengthwise of the drying surface and again cleaving thematerial at points intermediate the previous cleavings.

2. In combination a hearth, means for delivering material thereto at oneend, means for heating the hearth, and means for repeatedly cleaving"the material in a substantially vertical direction and advancing itthrough a small portion of the length of the hearth intermediate eachcleaving.

8. In combination a material supporting surface, a slidable elementmounted to reciprocate parallel to said surface a crosshead mounted tohave a limited sliding motion relative to said slidable element, a rake,means connecting the rake and said slidable element for supporting therake and raising and lowering the same, and means connecting thecross-head with said raising and lowering means.

4. In combination a material supporting surface, a slidable elementmounted to reciprocate parallel thereto, a cross-head The time requiredfor dryingdiifers with mounted to have a limited sliding motion relativeto said slidable element, a bell crank lever pivotally supported on saidslidable element, a connection from said cross head to one arm of saidbell crank lever, and a rake carrying member supported from the otherarm of said lever.

5. In combination, a material supporting surface, a bar or rod mountedto have sliding movement parallel to said surface, a cross-head mountedto have a limited sliding movement on said bar, a bell crank leverpivotally supported by said bar, an operating connection from one arm ofsaid crosshead to one arm of said bell crank lever, and a rake carryingelement supported from the other arm of said bell crank lever.

6. In combination, a material supporting surface, a bar or rod mountedto have a sliding movement parallel to said surface, a cross-headslidably supported by said bar, adjustable means for limiting thesliding movement of the cross-head on said bar, a bell crank leverpivotally mounted on said bar, a connection between said cross-head andone arm of the bell crank lever, and a rake carrying element supportedfrom the other arm of said bell crank lever.

7 In combination a material supporting surface, a bar or rod mounted toreciprocate arallel to said surface rides ri id v carried by said bar, across-head having oppositely extending members slidably sup ported bysaid guides, adjustable stops carried by said guides coacting with saidmembers to limit the sliding movement of the cross-head relative to saidbar or rod, a bell crank lever pivotally mounted on said bar or rod, anoperating connection between said cross head and one arm of said bellcrank lever, and a rake supporting element carried by the other arm ofsaid bell crank lever.

8. In combination, a material supporting surface, a bar or rod mountedto reciprocate parallel thereto, opposed socket members carried by saidbar or rod, a cross-head having oppositely extending parts slidablyguided in said socket members, set screws threaded through the ends ofsaid socket members and adapted to contact with the ends of thecrosshead parts to limit the movement of the cross-head relative tosaid. bar, a bell crank lever pivotally carried by said bar or rod,operating means connecting the cross-head with one arm of the bell.crank lever, and a rake supporting element connected to the other arm ofthe bell crank lever.

9. In combination amaterial supporting surface, a slidable elementmounted to reciprocate parallel to saidsurface, a crosshead mounted tohave a limited sliding movement relative to s '1 element, a bell cranklever pivotally carried by said slidable element, a connection from saidcrosshead to one arm of said bell crank lever, a rake supporting elementcarried by the other arm of said-bell crank lever, and a counterweighttending to rock said bell crank in opposition to the weight of the rake.

10. In combination a material supporting surface, a rod or barmounted toreciprocate parallel to said surface, a pair of bell crank leverspivotally supported by said bar, a cross-head mounted to have a limitedreciprocating movement relative to said bar with means for operating it,each ofsaid bell cranks having one arm extending substantiallyvertically and the other arm substantially horizontally, meansconnecting said cross-head with the vertically extend ing arms of thebell crank levers and a rake carrying frame supported from thehorizontally extending arms of said bell crank levers.

11. In combination a material supporting surface,'a rod or bar mountedto reciprocate parallel to said surface, a pair of bell crank leverspivotally supported by said bar, a cross-head mounted to have a limitedreciprocating movement relative to said bar with means for operating it,each of said bell cranks having one arm extending substantiallyvertically and the other arm substantially horizontally, meansconnecting said cross-head with the vertically extendmg arms of the bellcrank levers, a rake carrying frame, a rigid post member carried by onepart of said frame and pivotally connected to the horizontal arm of onebell crank lever, and flexible means connecting another part of saidframe with-the horizontal arm of the other bell crank lever.

12. In a conveying rake supported at a plurality of points, rigidlyattached means at one point for transmitting both vertical andhorizontal movements thereto, and flexibly attached means at anotherpoint for transmitting vertical movement without interfering with thehorizontal movement.

13. In aconveying rake supported at a plurality of points in its length,rigidly attached members at one point for transmitting both vertical andhorizontal movement, flexibly attached members at the other point orpoints for transmitting vertical movement, and means, adjustable as tolength of the horizontal movement, for operating.

14. A drying surface withina muffle, a rake in operative relationthereto, rake operating means outside the muffle, and movable means forsealing the opening in the muflie through which the moving parts extendagainst passage in or out of air, vapor or gas.

15. A muflie having a drying surface within the same, a rake inoperative relation to said surface, rake operating means outside of themuflie for moving the rake lengthwise of the muffle, said muflle havinglongitudinally elongated openings in its walls, said rake operatingmeans having parts extending through the openingsand connected with therakes, and slidable plates covering said openings.

16. A drying surface within a' muflie, a rake in operative relationthereto, means for imparting horizontal and vertical motion to the rakein a substantially rectangular closed path, and means outside the mufliefor adjusting the length of stroke of the rake.

17. In combination a hearth, a rake with means for imparting areciprocating motion thereto, and a deflector carried by said rakeadapted to receive material falling from above and deliver it to thehearth.

In testimony whereof, I aflix my signature.

HUGH B. LOW-DEN."

